Age-related processing strategies and go–nogo effects in task-switching: an ERP study

We studied cognitive and age-related changes in three task-switching (TS) paradigms: (1) informatively cued TS with go stimuli, (2) informatively cued TS with go and nogo stimuli, (3) non-informatively cued TS with go and nogo stimuli. This design allowed a direct comparison, how informative and non-informative cues influenced preparatory processes, and how nogo stimuli changed the context of the paradigm and cognitive processing in different aging groups. Beside the behavioral measures [reaction time (RT), error rate], event-related potentials (ERPs) were registered to the cue and target stimuli in young (N = 39, mean age = 21.6 ± 1.6 years) and older (N = 40, mean age = 65.7 ± 3.2 years) adults. The results provide evidence for declining performance in the older group: they had slower RT, less hits, more erroneous responses, higher mixing costs and decreased amplitude of ERP components than the participants of the younger group. In the task without the nogo stimuli young adults kept the previous task-set active that could be seen in shorter RT and larger amplitude of cue-locked late positivity (P3b) in task repeat (TR) trials compared to task switch trials. If both go and nogo stimuli were presented, similar RTs and P3b amplitudes appeared in the TR and TS trials. In the complex task situations older adults did not evolve an appropriate task representation and task preparation, as indicated by the lack of cue-locked P3b, CNV, and target-locked P3b. We conclude that young participants developed explicit representation of task structures, but the presence of nogo stimuli had marked effects on such representation. On the other hand, older people used only implicit control strategy to solve the task, hence the basic difference between the age groups was their strategy of task execution

Altered proactive control in adults with ADHD : evidence from event-related potentials during cued task switching

Cognitive control has two distinct modes - proactive and reactive (Braver, T. S. (2012). The variable nature of cognitive control: a dual mechanisms framework. Trends in Cognitive Sciences, 16(2), 105-112). ADHD has been associated with cognitive control impairments. However, studies have mainly focused on reactive control and not proactive control. Here we investigated neural correlates of proactive and reactive cognitive control in a group of adults with ADHD versus healthy controls by employing a cued switching task while cue informativeness was manipulated and EEG recorded. On the performance level, only a trend to generally slower responding was found in the ADHD group. Cue-locked analyses revealed an attenuated informative-positivity - a differential component appearing when contrasting informative with non-informative alerting cues - and potentially altered lateralisation of the switch-positivity - evident in the contrast between switch and repeat trials for informative cues - in ADHD. No difference in target-locked activity was found. Our results indicate altered proactive rather than reactive control in adults with ADHD, evidenced by less use of cued advance information and abnormal preparatory processes for upcoming tasks

Switch-independent task representations in frontal and parietal cortex

Alternating between two tasks is effortful and impairs performance. Previous fMRI studies have found increased activity in frontoparietal cortex when task switching is required. One possibility is that the additional control demands for switch trials are met by strengthening task representations in the human brain. Alternatively, on switch trials, the residual representation of the previous task might impede the buildup of a neural task representation. This would predict weaker task representations on switch trials, thus also explaining the performance costs. To test this, male and female participants were cued to perform one of two similar tasks, with the task being repeated or switched between successive trials. Multivoxel pattern analysis was used to test which regions encode the tasks and whether this encoding differs between switch and repeat trials. As expected, we found information about task representations in frontal and parietal cortex, but there was no difference in the decoding accuracy of task-related information between switch and repeat trials. Using cross-classification, we found that the frontoparietal cortex encodes tasks using a generalizable spatial pattern in switch and repeat trials. Therefore, task representations in frontal and parietal cortex are largely switch independent. We found no evidence that neural information about task representations in these regions can explain behavioral costs usually associated with task switching

Task-switching preparation across semantic and spatial domains: An event-related potential study

Previous event-related potential (ERP) studies have identified the specific electrophysiological markers of advance preparation in cued task-switching paradigms. However, it is not yet completely clear whether there is a single task-independent preparatory mechanism for task-switching or whether preparation for a switch can be selectively influenced by the domain of the task to be performed. To address this question, we employed a cued-task switching paradigm requiring participants to repeat or to switch between a semantic and a spatial task. The behavioural results showed a significant switch cost for both domains. The ERP findings, however, revealed that switch and repeat trials for semantic and spatial domains differed in the amplitude modulation of an early P2 and a sustained negativity both expressed over fronto-central scalp regions. Further differences between the two domains also emerged over posterior-parietal electrodes. This pattern of data thus shows that advance preparation in task-switching can be selectively modulated by the domain of the task to be performed

Context-specific activations are a hallmark of the neural basis of individual differences in general executive function

Common executive functioning (cEF) is a domain-general factor that captures shared variance in performance across diverse executive function tasks. To investigate the neural mechanisms of individual differences in cEF (e.g., goal maintenance, biasing), we conducted the largest fMRI study of multiple executive tasks to date (N = 546). Group average activation during response inhibition (antisaccade task), working memory updating (keep track task), and mental set shifting (number–letter switch task) overlapped in classic cognitive control regions. However, there were no areas across tasks that were consistently correlated with individual differences in cEF ability. Although similar brain areas are recruited when completing different executive function tasks, activation levels of those areas are not consistently associated with better performance. This pattern is inconsistent with a simple model in which higher cEF is associated with greater or less activation of a set of control regions across different task contexts; however, it is potentially consistent with a model in which individual differences in cEF primarily depend on activation of domain-specific targets of executive function. Brain features that explain commonalities in executive function performance across tasks remain to be discovered

Metacognitive processes in executive control development:The case of reactive and proactive control

Young children engage cognitive control reactively in response to events, rather than proactively preparing for events. Such limitations in executive control have been explained in terms of fundamental constraints on children’s cognitive capacities. Alternatively, young children might be capable of proactive control but differ from older children in their meta-cognitive decisions regarding when to engage proactive control. We examined these possibilities in three conditions of a task-switching paradigm, varying in whether task cues were available before or after target onset. Reaction times, ERPs, and pupil dilation showed that 5-year-olds did engage in advance preparation, a critical aspect of proactive control, but only when reactive control was made more difficult, whereas 10-year-olds engaged proactive control whenever possible. These findings highlight meta-cognitive processes in children’s cognitive control, an understudied aspect of executive control development

Effects of single-session transcranial direct current stimulation on reactive response inhibition

Transcranial direct current stimulation (tDCS) is widely used to explore the role of various cortical regions for reactive response inhibition. In recent years, tDCS studies reported polarity-, time- and stimulation-site dependent effects on response inhibition. Given the large parameter space in which study designs, tDCS procedures and task procedures can differ, it is crucial to systematically explore the existing tDCS literature to increase the current understanding of potential modulatory effects and limitations of different approaches. We performed a systematic review on the modulatory effects of tDCS on response inhibition as measured by the Stop-Signal Task. The final dataset shows a large variation in methodology and heterogeneous effects of tDCS on performance. The most consistent result across studies is a performance enhancement due to anodal tDCS over the right prefrontal cortex. Partially sub-optimal choices in study design, methodology and lacking consistency in reporting procedures may impede valid conclusions and obscured the effects of tDCS on response inhibition in some previous studies. Finally, we outline future directions and areas to improve research

Effect of aerobic exercise on the improvement of executive function in children with attention deficit hyperactivity disorder: a systematic review and meta-analysis

ObjectiveAerobic exercise (AE) interventions are beginning to be used as an emerging adjunctive treatment modality in the treatment of children with Attention Deficit Hyperactivity Disorder (ADHD). However, to date, there is no substantial evidence to support the improved effects of aerobic exercise intervention in children with ADHD aged 6–12 years. This study aims to investigate the effect of aerobic exercise therapy on executive function in children with attention deficit hyperactivity disorder aged 6–12 years.MethodWe conducted a systematic review and meta-analysis using PubMed and Web of Science. The cut-off date was June 1, 2023. The aim was to assess the impact of aerobic exercise interventions on children with ADHD and all randomized controlled trials eligible for aerobic exercise interventions for children with ADHD were included. Nine randomized controlled trials were screened for eligibility for systematic evaluation, and the nine studies were assessed for risk of bias using the PEDro score and the GRADE Quality of Evidence Evaluation System for quality grading of outcome indicators. After testing for heterogeneity, a random-effects model was selected for analysis. Finally, meta-analyses and regression analyses were performed on the core functions (inhibitory control, cognitive flexibility, and working memory) and subgroups of the nine studies on executive function using Revman 5.4 and Stata 16.0.ResultsThe risk of bias evaluation showed a mean PEDro score of 7.78, and of the nine studies, two were rated as having excellent methodological quality, while the remaining seven had a good level of evidence, and the GRADE evidence evaluation showed that the outcome indicators were all of moderate quality. Inhibitory control [SMD = 0.83,95% CI (0.37–1.29), Z = 3.51, p = 0.0005], cognitive flexibility [SMD = 0.65,95% CI (0.37–0.93), Z = 4.58, p < 0.00001], and working memory [SMD = 0.48,95% CI (0.02–0.95), Z = 2.03, p = 0.04] were statistically significant, with effect sizes of moderate or higher; furthermore, in subgroup analyses type of intervention, duration, intensity, and medication use had different effects on inhibitory control and cognitive flexibility, and the combined IC, CF statistic found that a single category of aerobic exercise (β = 0.867, p < 0.001), moderate intensity (β = 0.928, p < 0.001), 6–12 weeks (β = 0.804, p < 0.001), 60-90 min (β = 0.894, p < 0.001), and the use of medication (β = 1.202, p = 0.002) were better for overall improvement in EF.ConclusionAerobic exercise therapy significantly improved executive functioning in children with ADHD, showing above moderate effect sizes especially in inhibitory control, cognitive flexibility, and working memory. Aerobic exercise therapy can be used as a reference in improving executive function in children with ADHD, but given the limitations of this study, it should be used with caution when applied in clinical settings

Is performance in task-cuing experiments mediated by task set selection or associative compound retrieval?

Journal ArticleThis article may not exactly replicate the final version published in the APA journal. It is not the copy of record. The definitive version was published as: Forrest, C.L.D., Monsell, S., and McLaren I.P.L. (2014). Is performance in task-cuing experiments mediated by task-set selection or associative compound retrieval? Journal of Experimental Psychology: Learning, Memory and Cognition, 40, 1002-1024. http://dx.doi.org/10.1037/a0035981© 2014 American Psychological AssociationTask-cuing experiments are usually intended to explore control of task set. But when small stimulus sets are used, they plausibly afford learning of the response associated with a combination of cue and stimulus, without reference to tasks. In 3 experiments we presented the typical trials of a task-cuing experiment: a cue (colored shape) followed, after a short or long interval, by a digit to which 1 of 2 responses was required. In a tasks condition, participants were (as usual) directed to interpret the cue as an instruction to perform either an odd/even or a high/low classification task. In a cue + stimulus → response (CSR) condition, to induce learning of mappings between cue-stimulus compound and response, participants were, in Experiment 1, given standard task instructions and additionally encouraged to learn the CSR mappings; in Experiment 2, informed of all the CSR mappings and asked to learn them, without standard task instructions; in Experiment 3, required to learn the mappings by trial and error. The effects of a task switch, response congruence, preparation, and transfer to a new set of stimuli differed substantially between the conditions in ways indicative of classification according to task rules in the tasks condition, and retrieval of responses specific to stimulus-cue combinations in the CSR conditions. Qualitative features of the latter could be captured by an associative learning network. Hence associatively based compound retrieval can serve as the basis for performance with a small stimulus set. But when organization by tasks is apparent, control via task set selection is the natural and efficient strategy

Effekte transkranieller Gleichstromstimulation des Präfrontalkortex auf Aufmerksamkeit, Reaktionsinhibition und kognitive Flexibilität

Exekutive Funktionen (EF) dienen dem Menschen dazu, auf Reize schnell und adäquat zu reagieren und sich so in seiner Umwelt zurecht zu finden. Der linke dorsolaterale Präfrontalkortex (dlPFC) bietet dafür eine der wesentlichen funktionell-neuroanatomische Grundlage. Mit der transkraniellen Gleichstromstimulation (tDCS) besteht die Möglichkeit, nichtinvasiv Einfluss auf die kortikale Erregbarkeit zu nehmen. Diese Technik konnte schon bei gestörten EF genutzt werden, um diese zu verbessern. Ziel dieser Studie war es nun, bei gesunden Probanden die EF Reaktionsinhibition, kognitive Flexibilität und Daueraufmerksamkeit durch tDCS zu optimieren. In einem doppelverblindeten randomisierten cross-over Design erhielten 50 gesunde Probanden eine sham und eine verum Stimulation im Abstand von zwei Tagen. Stimuliert wurde anodal mit 1mA für 20 min am linken dlPFC. Die Referenzelektrode wurde kontralateral supraorbital fixiert. Zur Testung der EF wurde der Parametric Go/No-Go (PGNG) Test verwendet, zudem wurde mithilfe eines Fragebogens (Positive and Negative Affect Schedule; PANAS) die momentane Stimmung vor und nach der Stimulation erhoben. In keinem der Zielparameter zeigten sich signifikante Unterschiede zwischen den Leistungen während verum- und sham-tDCS. Ferner wurde die Stimmung nicht von der Stimulation beeinflusst. Es sind keine gravierenden Nebenwirkungen aufgetreten und keiner der Probanden hat den Versuch abgebrochen. Die Studie kann die in anderen Studien gezeigte Wirkung der tDCS auf EF bei gesunden Probanden nicht bestätigen. Sie zeigt auf, wie wichtig es ist, weitere Parameter zu finden, die im Voraus Aufschluss auf die Effekte der Stimulation liefern können